Method for determining asymmetrical condition i.e. rod breakage, in rotor of e.g. three-phase asynchronous motor, involves determining asymmetrical condition in rotor during existence of side bands in current spectrum

摘要

The method involves determining pitch of side bands of current frequency in a frequency spectrum of the current of the phase of an electrical machine. An asymmetrical condition in the rotor is determined during existence of the side bands in a current spectrum, which is received by a Pearson transformer (1). Slippage of the rotor is calculated under application of the frequency of certain side bands. Amplitude values of the bands are stored and compared with existing amplitude values at a time point. The amplitude values are stored as calibration values, before the operation of the machine. An independent claim is also included for an electrical machine that is equipped with control electronics for determining asymmetrical condition in the rotor of an electrical machine.